Chapter 4. Ways in Which Evolution Helps Describe the Mind

I actually, in my own work, think evolution can tell us some interesting things. And I want to try to make a case for ways in which evolution can inform and enlighten us about the mind as it is.

First, I want to make a point, which is although this course is Intro Psych and it is about the mind as it is, still I think by any account the evolution of consciousness, morality and so on, just is intuitively interesting. It's the sort of thing that people are just fascinated by and I think it's a question of interest in and of its own right. But here's how it could tell us about psychology. For one thing, it can tell us what can be innate and what cannot. So, some problems, some evolutionary problems, have been around for a long time and could lead to special biological adaptations. If I told you there is a biological adaptation for talking, mate selection, childcare; maybe it's true, maybe it isn't, but it's not crazy. From an evolutionary point of view, it's a reasonable possibility that it is.

Other problems are recent and our brains could not be specialized to deal with them: written communication, interacting with strangers, driving a car, playing chess. If you were to argue that there's a part of the brain devoted to playing chess, I would say you're utterly wrong. You cannot be right because, from an evolutionary point of view, there could be no such part of the brain evolved because playing chess is a recent innovation. As a result, a focus on evolution could help discipline us to make coherent claims about what is built-in and what isn't built-in.

Third, we're going to talk about human differences in this course. We're going to devote a class to human differences of the sort of what makes you different from her, different from her. Why do we have different intelligences in this class? Why are some of us arrogant and some of us humble? Some of us like — attracted to men, others attracted to women, and so on. But there's also questions of group differences. And evolutionary theory can help us say intelligent things about what sort of group differences you should expect because evolutionary theory predicts that some populations should evolve in different ways than others.

The most obvious example is that children should be different from adults. The evolutionary problems faced by a child are very different from the evolutionary problems faced by an adult. And you can make specific and rather interesting predictions about how children's brains should different — differ from adults' brains. Evolutionary theory predicts — does not make any predictions about racial differences or ethnic differences. Some might exist, but there's no adaptive reason why humans who have evolved in different parts of the world should have profound differences in their mental capacities.

What does evolutionary theory say about sex differences? Well, it says some interesting things, and we're going to devote a class to discussing them, but what I think is going to be true — proved to be important is that we'll be able to use evolutionary biology to talk sensibly about what sort of distinctions between the sexes, between males and females, one would expect to find and what sort one wouldn't expect to find. We can make educated predictions. I'm going to have — I want to put here a clip of a man. This is a scene from a movie, the movie "Roger Dodger," that begins with a man making quasi-evolutionary claims about the differences between men and women. And I want to put this as an example of what you could call "barroom evolutionary psychology." And I want us to hold this in our minds because we're going to return to these claims and discuss their validity. [clip playing]

I like this for a few reasons. First, I like the backward reference to William James and utility. Second, it is a gorgeous combination of some things that are actually reasonably rational and total bull crap. And — but what evolutionary biology will give us is the tools to distinguish between the two. On the face of it immediately, the ability to read maps, the claim that that has a biological — that differences in that ability have a biological root is crazy. On the other hand, the claim that one — that males may develop a trait not because it's advantageous but to attract females is less crazy. The telepathic stuff is really crazy but —;So, I'm not at this point — We're going to devote a lecture to sex. I do not, at this point, want to make any claims one way or another. But what I want to suggest is that from a biological point of view we could say sensible and intelligent things about what differences should exist and what shouldn't.

Finally, and most of all, looking at something from the perspective of design, the perspective of what's it for, can often give you interesting insights as to its current nature. And I'll give you two quick examples, one that's not from psychology, one that is. Women suffer — Often women who are pregnant early in their pregnancy suffer from morning sickness, nausea, throwing up and so on. This has traditionally been viewed as just a breakdown in the system — too much hormones, everything's askew; women get nauseous. Margie Profet suggested an alternative and this won her the MacArthur Genius Award. And this was the claim that maybe pregnancy sickness is not an accident; rather, it's designed, it has a biological purpose. In particular, as the baby develops in the uterus, it is vulnerable to various sorts of poisons or teratogens. Profet suggested that pregnancy sickness is a hypersensitive period where women are extremely sensitive, get extremely nauseous towards the sorts of foods that could damage their baby.

Now, if she just ended there it's a story. How do we know it's true? But then she went on to examine it the same way that any scientist examines any claim – by making predictions and testing them. And this makes some interesting predictions. It suggests the timing of onset and offset of pregnancy sickness, of morning sickness, should correspond to the period of maximal vulnerability on the part of the developing embryo or fetus. Suggested the types of foods avoided should correspond to those sorts of foods that were most deadly for the fetus and that were deadly for the fetus during the periods where humans evolved. This last qualification is an important one. Women do not develop an aversion to alcohol during pregnancy even though alcohol is extremely dangerous to the developing child. The answer is an easy one. Alcohol wasn't around during our evolutionary history and we could not have evolved a system to protect ourselves from it.

And finally, there should be a relationship between miscarriage and birth defects in a surprising direction. For Profet, and she has evidence to back this up, pregnancy sickness is not a glitch in the system. Rather, it's the sign of a healthy act of protective mechanism going on. And in fact, the more morning sickness the more the baby should be protected. Something which, by and large, appears to be true. That's an example of how the question — when dealing with this they say, "Hey. Women throw up when they get pregnant" and then say, "Look. Maybe that's not just a glitch. What's it for?" You could then learn some interesting things.

Here's a different example based on the last lecture, this wonderful lecture by Peter Salovey on sex and love where he talked about the "big three." These are the "big three" to remind you of what attracts us to somebody else. You are very attracted to the person next to you or a person that — because of proximity, similarity, familiarity. And there is abundant evidence supporting the truth of this. It's almost always true but the evolutionary psychologist looks at this and says there's something seriously wrong here. There are some cases where that has to be totally, absolutely mistaken. To realize what this is, think for a moment. What humans are you most close to, most similar to and most familiar with? What humans did you spend over ten years of your life with who are genetically and environmentally as close to you as if they were related, who you are intimately familiar with? Are those the humans that you find the hottest? [laughter] No. They're your siblings and they are not hot. [laughter]

I was on Google Images this morning. I put up some hot siblings and — but — although we may find them hot, they do not typically, with some rare and bizarre exceptions, find [laughter] one another hot. Why not? Well, this is not a huge puzzle from the standpoint of evolutionary biology. Evolutionary biology posits that humans, as well as other animals, should have incest avoidance. We should love — we should be attracted to those familiar to us, similar to us, close to us, but not kin. Kin are off limits. There is a good reason why. Because if you inter-mate with your kin you have bad offspring [laughter] and so animals should be wired up not to mate with their kin. And in fact, this is what happens.

There are — Parents of teenagers have all sorts of concerns. And a lot of the concerns are, in fact, sexual. How do you keep your son and/or your daughter from going out and having sex with too many people, or the wrong people, or unprotected sex? But there are no parenting guides in the world that say "How do you keep your children from having sex with one another?" [laughter] You typically do not need to because they do not want to have sex with one another.

Now, this is — actually also illustrates the difference between proximate and ultimate causation. So, you think for yourself, "Eew. Do I want to have sex with my sister?" You don't think to yourself, "I would prefer not to, for the offspring that we will create will be nonviable and it'll be a waste of my reproductive efforts." Rather, you think, "Eew," because at a gut level you respond. And this sort of instinctive response is what you get from an evolutionary analysis of sex.

But this story is deeply incomplete because the question that gets raised is "how do you tell?" You don't want to have sex with your kin but how do you tell your kin? People don't carry their DNA markers on strips that you could see. How do you tell who your kin are? And this actually turns out to be a really interesting question. It used — And some research suggests that the answer is simple. You avoid sex with people you grew up with. And these studies actually come from kibbutz studies, studies where people are raised communally on an Israeli kibbutz. They know they're not related, but still, the fact that they were raised together as kids suggests that there's a cue at a gut level not to be attracted to one another.

It turns out there's some reason now to believe this story is incomplete. A paper that came out in Nature five days ago reported a series of extremely interesting studies. And they found that the cue of being raised together as a child with somebody — yes, that does diminish sexual desire, but an even bigger cue was "did you observe your parents, and in particular, your mother, taking care of that person?" If you did, that seriously diminishes sexual desire and brings it down to the level of disgust. And again, these are the sort of questions and issues you begin to ask when you approach things from an evolutionary perspective. Okay.

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